Some years aqo processes were developed for producing fibrous batts by contacting fibers with a dry fiber-binder based on certain thermoplastic polymers. Such processes are described in the following U.S. Patents among others:
Buck et al U.S. Pat. No. 3,993,518, "Buck '518"; PA1 Buck et al U.S. Pat. No. 3,997,942, "Buck '942"; PA1 Buck et al U.S. Pat. No. 4,047,991, "Buck '991"; PA1 Buck et al U.S. Pat. No. 4,050,997, "Buck '997"; PA1 Buck et al U.S. Pat. No. 4,051,294, "Buck '294"; PA1 Buck et al U.S. Pat. No. 4,053,673, "Buck '673"; PA1 Buck et al U.S. Pat. No. 4,053,674, "Buck '674"; PA1 Buck U.S. Pat. No. 4,211,817, "Buck '817"; PA1 Buck et al U.S. Pat. No. 4,363,680, "Buck '680"; PA1 Buck U.S. Pat. No. 4,550,050, "Buck '050"; PA1 Buck U.S. Pat. No. 4,457,793, "Buck '793"; PA1 Buck et al U.S. Pat. No. 4,473,428, "Buck '428"; and PA1 Elsen U.S. Pat. No. 4,869,950, "Elsen".
These prior processes became commercially successful in the Unites States of America and in a number of overseas countries because of their advantages over the prior art, as set forth in the above patents. However, over the ten or fifteen years of their widespread use the cost of the polyvinylidene-polyvinyl chloride copolymer ("PVDC/PVC copolymer") used in these processes increased dramatically so that these processes became uneconomic. For several years scrap PVDC/PVC copolymers were available but eventually the supply of these materials became insufficient to satisfy the market. In addition certain disadvantages associated with the use of PVDC/PVC copolymers and other chlorinated materials, including corrosion of equipment, restricted the use of these materials in certain applications. Since the PVDC/PVC copolymers were thermoplastic, they suffered from an additional disadvantage in that they could not be hot molded into certain shaped articles useful for example as automobile insulating products.
More recently a new type of dry powder bonding system was developed by this inventor as described in Buck U.S. Pat. No. 5,804,005, (Buck '005) and in Buck U.S. Pat. No. 6,039,821 (Buck '821) and in a number of foreign countries which are signatory to the Patent Cooperation treaty ("PCT"). Several other patents based on the same or similar chemistry are currently pending. Buck '005 and Buck '821 employ epoxy polymers in dry powder form which when distributed throughout a fibrous batt can be advanced to high molecular weights and cured to either the B stage or more fully cured to the C stage by processing methods described in these two patents. The B stage products may be molded into various shapes in a heated mold such as is used to mold phenolic polymers and certain other thermosetting polymers. In order to maintain firmness during and immediately after the hot molding process which may be carried out at 200.degree. to 230.degree. C., catalysts and agents which cause the epoxide chain molecules to cross link with each other must be employed. Examples include trimelletic anhydride, tetracarboxy benzene dianhydride, and other multi-functional cross-linking agents. These agents are quite expensive, however, and even they do not raise the glass transition temperature (T.sub.g) of the epoxide polymer sufficiently to hold the molded batt in a firm and rigid position immediately upon its removal from the molding press.
The epoxide polymers themselves are relatively expensive; the cross-linking agents are even more costly; and the results of hot molding are not equivalent to those obtained with phenol formaldehyde or novalac polymers. Consequently these epoxide bonded and molded products, while having the desirable advantages of freedom from phenol or formaldehyde, are not competitive in the market place. In fact, while the process of Buck '005 has achieved commercial success in the USA and a number of other countries, the commercial products have been based on scrap powder paint with an epoxide base. Powders formulated from these materials function very effectively in flat cushion batts and semi-compressed materials and possess many advantages over earlier technologies, including freedom from chlorine, from phenol, from formaldehyde, and from other undesirable bi-products. The batts made from scrap powder paint, which compete effectively with phenolic and novalac polymers in flat, non-molded fibrous batts cannot be molded with the rigidity obtainable with the phenolic polymers.